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N-glycosylation site occupancy in serum glycoproteins using multiple reaction monitoring liquid chromatography-mass spectrometry


Hülsmeier, A J; Paesold-Burda, P; Hennet, T (2007). N-glycosylation site occupancy in serum glycoproteins using multiple reaction monitoring liquid chromatography-mass spectrometry. Molecular & Cellular Proteomics, 6(12):2132-2138.

Abstract

Congenital disorders of glycosylation (CDGs) are a family of N-linked glycosylation defects associated with severe clinical manifestations. In CDG type-I, deficiency of lipid-linked oligosaccharide assembly leads to the underoccupancy of N-glycosylation sites on glycoproteins. Although the level of residual glycosylation activity is known to correlate with the clinical phenotype linked to individual CDG mutations, it is not known whether the degree of N-glycosylation site occupancy by itself correlates with the severity of the disease. To quantify the extent of underglycosylation in healthy control and in CDG samples, we developed a quantitative method of N-glycosylation site occupancy based on multiple reaction monitoring LC-MS/MS. Using isotopically labeled standard peptides, we directly quantified the level of N-glycosylation site occupancy on selected serum proteins. In healthy control samples, we determined 98-100% occupancy for all N-glycosylation sites of transferrin and alpha(1)-antitrypsin. In CDG type-I samples, we observed a reduction in N-glycosylation site occupancy that correlated with the severity of the disease. In addition, we noticed a selective underglycosylation of N-glycosylation sites, indicating preferential glycosylation of acceptor sequons of a given glycoprotein. In transferrin, a preferred occupancy for the first N-glycosylation site was observed, and a decreasing preference for the first, third, and second N-glycosylation sites was observed in alpha(1)-antitrypsin. This multiple reaction monitoring LC-MS/MS method can be extended to multiple glycoproteins, thereby enabling a glycoproteomics survey of N-glycosylation site occupancies in biological samples.

Congenital disorders of glycosylation (CDGs) are a family of N-linked glycosylation defects associated with severe clinical manifestations. In CDG type-I, deficiency of lipid-linked oligosaccharide assembly leads to the underoccupancy of N-glycosylation sites on glycoproteins. Although the level of residual glycosylation activity is known to correlate with the clinical phenotype linked to individual CDG mutations, it is not known whether the degree of N-glycosylation site occupancy by itself correlates with the severity of the disease. To quantify the extent of underglycosylation in healthy control and in CDG samples, we developed a quantitative method of N-glycosylation site occupancy based on multiple reaction monitoring LC-MS/MS. Using isotopically labeled standard peptides, we directly quantified the level of N-glycosylation site occupancy on selected serum proteins. In healthy control samples, we determined 98-100% occupancy for all N-glycosylation sites of transferrin and alpha(1)-antitrypsin. In CDG type-I samples, we observed a reduction in N-glycosylation site occupancy that correlated with the severity of the disease. In addition, we noticed a selective underglycosylation of N-glycosylation sites, indicating preferential glycosylation of acceptor sequons of a given glycoprotein. In transferrin, a preferred occupancy for the first N-glycosylation site was observed, and a decreasing preference for the first, third, and second N-glycosylation sites was observed in alpha(1)-antitrypsin. This multiple reaction monitoring LC-MS/MS method can be extended to multiple glycoproteins, thereby enabling a glycoproteomics survey of N-glycosylation site occupancies in biological samples.

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Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > Center for Integrative Human Physiology
04 Faculty of Medicine > Institute of Physiology
07 Faculty of Science > Institute of Physiology

04 Faculty of Medicine > University Children's Hospital Zurich > Medical Clinic
Dewey Decimal Classification:570 Life sciences; biology
610 Medicine & health
Language:English
Date:December 2007
Deposited On:19 Mar 2009 16:30
Last Modified:05 Apr 2016 13:03
Publisher:American Society for Biochemistry and Molecular Biology
ISSN:1535-9476
Additional Information:This research was originally published in Hülsmeier, A J; Paesold-Burda, P; Hennet, T (2007). N-glycosylation site occupancy in serum glycoproteins using multiple reaction monitoring liquid chromatography-mass spectrometry. Molecular & Cellular Proteomics, 6(12):2132-2138. © the American Society for Biochemistry and Molecular Biology.
Publisher DOI:10.1074/mcp.M700361-MCP200
PubMed ID:17823199
Permanent URL: http://doi.org/10.5167/uzh-14439

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